Resolve "Authenticated / Admin GraphQL complexity limits are not being applied"

app/graphql/gitlab_schema.rb

@@ -31,9 +31,10 @@ class GitlabSchema < GraphQL::Schema
 
   class << self
     def multiplex(queries, **kwargs)
-      kwargs[:max_complexity] ||= max_query_complexity(kwargs[:context])
+      kwargs[:max_complexity] ||= max_query_complexity(kwargs[:context]) unless kwargs.key?(:max_complexity)
 
       queries.each do |query|
+        query[:max_complexity] ||= max_query_complexity(kwargs[:context]) unless query.key?(:max_complexity)
         query[:max_depth] = max_query_depth(kwargs[:context])
       end
 

spec/requests/api/graphql/gitlab_schema_spec.rb

@@ -125,9 +125,9 @@ RSpec.describe 'GitlabSchema configurations' do
 
     subject do
       queries = [
-        { query: graphql_query_for('project', { 'fullPath' => '$fullPath' }, %w(id name description)) },
-        { query: graphql_query_for('echo', { 'text' => "$test" }, []), variables: { "test" => "Hello world" } },
-        { query: graphql_query_for('project', { 'fullPath' => project.full_path }, "userPermissions { createIssue }") }
+        { query: graphql_query_for('project', { 'fullPath' => '$fullPath' }, %w(id name description)) }, # Complexity 4
+        { query: graphql_query_for('echo', { 'text' => "$test" }, []), variables: { "test" => "Hello world" } }, # Complexity 1
+        { query: graphql_query_for('project', { 'fullPath' => project.full_path }, "userPermissions { createIssue }") } # Complexity 3
       ]
 
       post_multiplex(queries, current_user: current_user)
@@ -139,10 +139,9 @@ RSpec.describe 'GitlabSchema configurations' do
       expect(json_response.last['data']['project']).to be_nil
     end
 
-    it_behaves_like 'imposing query limits' do
-      it 'fails all queries when only one of the queries is too complex' do
-        # The `project` query above has a complexity of 5
-        allow(GitlabSchema).to receive(:max_query_complexity).and_return 4
+    shared_examples 'query is too complex' do |description, max_complexity|
+      it description, :aggregate_failures do
+        allow(GitlabSchema).to receive(:max_query_complexity).and_return max_complexity
 
         subject
 
@@ -155,9 +154,15 @@ RSpec.describe 'GitlabSchema configurations' do
         # Expect errors for each query
         expect(graphql_errors.size).to eq(3)
         graphql_errors.each do |single_query_errors|
-          expect_graphql_errors_to_include(/which exceeds max complexity of 4/)
+          expect_graphql_errors_to_include(/Query has complexity of 8, which exceeds max complexity of #{max_complexity}/)
+        end
       end
     end
+
+    it_behaves_like 'imposing query limits' do
+      # The total complexity of the multiplex query above is 8
+      it_behaves_like 'query is too complex', 'fails all queries when only one of the queries is too complex', 4
+      it_behaves_like 'query is too complex', 'fails when all queries combined are too complex', 7
     end
 
     context 'authentication' do

spec/requests/api/graphql_spec.rb

@@ -208,6 +208,49 @@ RSpec.describe 'GraphQL' do
     end
   end
 
+  describe 'complexity limits' do
+    let_it_be(:project) { create(:project, :public) }
+    let!(:user) { create(:user) }
+
+    let(:query_fields) do
+      <<~QUERY
+      id
+      QUERY
+    end
+
+    let(:query) do
+      graphql_query_for(
+        'project',
+        { 'fullPath' => project.full_path },
+        query_fields
+      )
+    end
+
+    before do
+      stub_const('GitlabSchema::DEFAULT_MAX_COMPLEXITY', 1)
+    end
+
+    context 'unauthenticated user' do
+      subject { post_graphql(query) }
+
+      it 'raises a complexity error' do
+        subject
+
+        expect_graphql_errors_to_include(/which exceeds max complexity/)
+      end
+    end
+
+    context 'authenticated user' do
+      subject { post_graphql(query, current_user: user) }
+
+      it 'does not raise an error as it uses the `AUTHENTICATED_COMPLEXITY`' do
+        subject
+
+        expect(graphql_errors).to be_nil
+      end
+    end
+  end
+
   describe 'keyset pagination' do
     let_it_be(:project) { create(:project, :public) }
     let_it_be(:issues) { create_list(:issue, 10, project: project, created_at: Time.now.change(usec: 200)) }